Hydroforming with preliminary desulfurizing of the naphtha feed



. A. B. WELTY, JR 2,898,287 HYDROFORMING WITH PRELIMINARY DESULFURIZING Aug. 4, 1959 OF THE NAPHTHA FEED 2 Sheets-Sheet Filed Oct. 20., 1953 S.. mm

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ALBERT B.WEI TY, JR. BY

INVENTOR ATTORNEY HYDRoFoRMING WITH PRELIMINARY DESUL- FURIZING on THE NAPHTHAFEED Albert B. Welty, Jr., Westfield, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware Application October 20, 1953, Serial No. 387,097

3 Claims. 7 (Cl. 208-89) The present invention relates to improvements in hydroforming. More particularly, the present invention relates to hydroforming a feed stock containing sulfur in the presence of a platinum group metal catalyst.

Hydroforming is an operation in which naphtha, either virgin, cracked, Fischer or a mixture of them, is contacted at elevated temperatures and pressures with a solid catalytic material in the presence of hydrogen. As ordinarily operated, there is no net consumption of hydrogen in this hydroforming process, and usually thereis a net production of hydrogen.

It is generally known that sulfur found in the naphtha feed causes deactivation of the platinum group metal catalysts. Heretofore, and prior to the present invention, when hydroforming a naphtha stock containing sulfur, it was customary to subject the naphtha feed stock to hydrodesulfurization using a. conventional hydroforrning unit. In this operation the naphthais contacted at elevated temperatures with a catalyst such as cobalt molybdate and added hydrogen, whereby the sulfur contained in the feed is converted to H 8. Following the hydrodesulfurization treatment, the product is cooled to a temperature of about 100 F. and then stripped to remove the H 8 formed during the; hydroforming step. This operation requires reheating the desulfurized feed stock in order to prepare the feed for the hydroforming operation. This reheating step, therefore, increases the amount of heat exchange surface and furnace capacity required for the complete process of hydroforming the desulfurized feed. a I 1 In brief compass, the present invention cures the insufiiciencics and disadvantages of the above-indicated, .two-step process by (l) employing a fluidized desulfurization catalyst which absorbs the sulfur removed, thus giving a substantially H S-free naphtha product and (2) passing'the uncooled desulfurized naphtha to the hydroforming stage thus saving cooling surfaces and furnace capacity for reheating.

The sulfur-containing catalyst used in the desulfurization step is continuously withdrawn therefrom and passed to a relatively small-sized regenerator wherein it is treated with an oxygen-containing gas to remove the sulfur as the oxides of sulfur whereupon the regenerated catalyst is returned after reduction to the desulfurizing step. Thus, the sulfur contained in the feed is taken up by the catalyst during desulfurization and none of the sulfur is converted to H 8 so that the feed to the hydroforming step is free of this material.

The object of the invention is to hydrodesulfurize a naphtha feed prior to hydroforming the feed stock, in the presence of a platinum group metal characterized in that the desulfurized stock is passed uncooled to the hydroforming stage. 7

Another object of the present invention is to hydroform naphtha originally containing substantial amounts of sulfur under conditions such that the sulfur is removed prior to the hydroforming operation by means which are efiicient and relatively inexpensive.

2,898,281 Patented Aug. 4, 1959 Another object of the present invention is to desulfurize a sulfur-containing naphtha under conditions such that substantially no H 8 is formed, and thereafter to treat the desulfurized product under hydroforming conditions with a platinum group metal catalyst in a process characterized in that important economies are eifected in the complete process in the matters of equipment and in which a preferred modification of the present invention may be carried into eifect.

Referring in detail to the drawing, 1 represents. a desulfurizing reactor containing a bed of fluidized catalyst C extending from a foraminous member G which acts as a gas distributing means to an upper dense phase level L; 2 represents a desulfurizing catalyst regenerator in which regenerator catalyst containing sulfur is formed into a second dense fluidized =bed C disposed in said regenerator between a grid or screen G to an'upper dense phase level L and therein treated with an oxygencontaining gas to remove said sulfur; and 3 represents a reducer containing a third dense phase fluidized bed of a regenerated catalyst C extending from a grid or screen G to an upper dense phase level L In this reducer the regenerated catalyst is treated with a hydrogen-containing gas.

In operation, a naphtha feed boiling substantially within the range of from 200400 F., enters the present system through line 4 (Fig. 1B) and thence passes through a heat exchanger 5 wherein itis heat exchanged with a hot hydroformed product more fully referred to hereinafter, whereupon it is withdrawn from the heat exchanger 5 through line 6, then passed through a furnace 7 wherein it is .further heated to a temperature of about 800 F., and thence passed via line 8 into the bottom of reactor 1.' Meanwhile, a hydrogen-containing gas obtained from the product recovery system is heated in a furnace 11 and then passed via line 12 to desulfurizer reactor 1.

Under conditions more fully set forth hereinafter, the desired hydrodesulfurization occurs, and the mixture of hydrogen and desulfurized oil vapors emerge from the dense fluidized bed C, thence pass through a light or dilute suspension of catalyst in gasiform material which extends from L to the top of reactor 1. In this space, catalyst is separated or disengaged from the upflowing gasiform material. Before the gasiform material is withdrawn from reactor 1, it is forced through one or more cyclones S wherein catalyst still entrained in said vapors of gasiform material is separated therefrom and returned to the dense fluidized bed through one or more dippipes d. The gasiform material is withdrawn from the hydrodesulfurization vessel 1 overhead via line 13 and thence passed through two or more gas-solids separating devices S and S wherein further quantities of entrained catalyst are separated from the gasiform material in line 13. The gasiform material substantially free of sulfur and catalyst is then passed via line 14 to the hydroforming section and therein treated as more fully set forth hereinafter.

Referring again to reactor 1, sulfurized catalyst is withdrawn therefrom through line 15 and passed into a receiver 16 where it is treated with steam introduced through line 17 to remove for recovery in means (not shown) feed oil adsorbed 'or occluded by said catalyst. The thus treated catalyst is then withdrawn from receiver 16 through line 18 carrying control valve 19 and charged into line 22. Air or other oxygen-containing gas is inand carries it in suspension into regenerator 2.

7 containing gas and the result of this treatment is to convert a part of the sulfur into sulfur oxides which are removed overhead. The regenerated catalyst is then withdrawn from regenerator 2 through line 23 wherein it is treated with stripping steam introduced through line 24. Line 23 is provided with flow control valve 25. The stripped catalyst in line 23 is then charged into line 26 containing recycle gas, that is, hydrogen-containing gas recovered from the product recovery system of the hydroforming section referred to previously. In line 26 the stripped catalyst is formed into a suspension and then conducted to reducer 3 wherein it is formed into a fluidized bed extending from G to L and treated under conditions more fully set forth hereinafter to reduce the said catalyst. Overhead from reducer 3 there is recovered water, H 8 and low molecular weight hydrocarbons through line 27. The reduced catalyst is then withdrawn from reducer 3 through standpipe 28 controlled by valve 29 and charged into the heated oil feed in line 8 for return to reactor 1. Prior to charging the catalyst into oil feed line 8, catalyst may be stripped with steam which is charged to the bottom of standpipe 28 through line 30.

With respect to reducer 3, the exit gas may be forced through one or more cyclones to remove entrained catalyst but preferably the cyclones may be omitted to permit catalyst fines to be removed from the system at this point thus reducing the danger of this catalyst from passing over into the hydroforming section wherein it might injure the platinum catalyst therein used.

Referring again to regenerator 2, the sulfur oxides withdrawn overhead are passed into an outside cyclone S wherein entrained catalyst is removed from the fumes. This removed catalyst may be rejected from the system through line 32, or it may, at least in part, be returned to regenerator 2 via line 33.

As previously indicated the desulfurized hot oil vapors and hydrogen in line 14 are passed to a hydroforming section shown in Fig. 1B. In this section the said oil vapors and hydrogen are first further heated in a furnace 34 and thence passed via line 35 to the first of a series of reactors each containing a fixed bed of platinum catalyst. This catalyst may comprise say 0.05 to 2 weight percent platinum carried on 98 to 99.05 weight percent alumina. Palladium may be substituted for the platinum although the amount of the former, since it is a much less active catalyst, must be present in the catalyst composition to about three times the percentage composition specified above for platinum.

Thus, the heated gasiform material in line 35 is charged into the top of hydroforming reactor where under conditions of temperature, pressure and feed rate, the desired conversion occurs. The reaction is endothermic in reactor 36 and an effluent containing unreacted material is withdrawn from the bottom of reactor 36 via line 37 and forced through a second furnace 38 wherein the oil and hydrogen are reheated and thence passed through a second reactor 39 wherein further conversion occurs, as well as a temperature drop. The reactants are withdrawn from reactor 39, through line 40, reheated in furnace 41 and thence passed via line 42 into a third reactor 43 wherein the reaction is substantially completed. The

raw product is withdrawn from reactor 43, passed through heat exchanger 5, thence passed to a cooler wherein the product is further cooled, and thence passed to a separator 45. A gas rich in hydrogen is withdrawn overhead from separator 45 and passed via line 9 into a furnace 11 wherein the hydrogen containing gas is reheated and thence recycled via line 26 to the desulfurizing re- 4 actor 1. Excess gas may be withdrawn from line 9 through line 10 and rejected from the system.

The raw hydroformate product is withdrawn from separator 45 and distilled and fractioned in a conventional manner in 46 and then delivered to receiver 47.

In order further to explain the present invention the following conditions in the principal parts of the system shown in the drawing are set forth immediately following.

CONDITIONS IN DESULFURIZER 1 Range Preferred Catalyst (Composition) Catalyst (particle size distribution) Temperature, F 700-900 800 Pressure, p.s.i.g 50-900 200 Cubic feet Hz per bbl. of oil fedto reactor- 200-5, 000 1, 000 Cone. of H in Hz gasVol. percent -98 Feed rate oil, w./hr./w %2 Superficial Gas Velocity ond 0.3-2.0 0.75

CONDITIONS IN REGENERATOR 2 Temperature, F 900-1, 100 960 Pressure, p.s.i.g. 50-900 200 Contact Time in seconds... 5-100 40 Superficial Gas Velocity, ft./s $-3 1.0 0, Concentration in regeneration gas 21%.

CONDITIONS IN REDUOER 3 Temperature, F 910-1, 100 970 Pressure, p.s i g-.- 50-900 200 Contact Time in sec 5-100 40 Cone. H; in Treating Gas-V 80-98 05 Superficial Gas Velocity, ft./sec 0.3-2.0 0.75

CONDITIONS IN HYDROFORMERS 36, 39 AND 43 Catalyst: Pt on A1 0 weight percent Pt based on total weight catalyst 0. 005-2 0.10-1. 0 Inlet temperature, F.- 870-1, 000 900 Outlet temperature, F 800-890 2 800, 830,870 Pressure in p.s.i.g-...- 50-900 1 500 Contact time in second 5-150 40 Standard cubic feet of H7 per bbl. of oil fed to reactor 500-5, 000 1, 000 Cone. of Hg in Hz containing gas 90-98 1 Gas velocity assuming no catalyst in reactor. First, second and third reactors respectively.

Before charging to reactor 39 the effluent from reactor 36 is reheated to a temperature of about 900 F. The effiuent from reactor 39 is at a temperature of about 830 F. and this is reheated to about 900 F. before charging to the third reactor from which it is withdrawn at a temperature of about 870 F. All three hydroforming reactors contain the same catalyst and except for the temperature differences noted above and the ensuing pressure drop occasioned as the oil is passed through the series of reactors, conditions in the several hydroforming reactors are substantially the same.

With the passage of time the platinum catalyst in the several hydroforming reactors will require regeneration due to the deposition of carbonaceous material thereon. This may be done by discontinuing the flow of oil through the hydroforming reactors and passing diluted air therethrough at a temperature of about l058ll00 F. to burn off the contaminating deposits. The regeneration is carried out at system pressure, preferably. The oxygen concentration of the regeneration gas may be, say, about 2% but may be increased to 21% or higher during the final phase of the regeneration. However, conditions 'must be adjusted to prevent heating the catalyst above about 1l00 F. If the said regeneration of the catalyst after several cycles of 'on-stream and regeneration periods' is not restored to its original activity, the catalyst may be rejuvenated by treatment with air or oxygen for 2 to 24 hours at, say, 1060 to 1100 F. while under a pressure of 75 p.s.i.g. or higher. In extreme cases where a combination of regeneration and rejuvenation fails to restore catalyst activity to a satisfactory activity level, it may be treated in situ with a mixture of aqueous nitric acid and aqueous hydrochloric acid a 50-200 F.,'or by chlorine in a dry gas stream, such as air at 600-1000 F., whereupon the catalyst activity is restored.

A number of runs were made to test the efliciency of the hydrodesulfinization reactor represented by 1 in Fig. 1A of the accompanying drawing. The conditions and results obtained during these runs were set forth in the below tabulation:

Desulfurization operation transferring the catalyst to a regeneration zone and therein treating the catalyst withan oxidizing gas to remove sulfur from the catalyst, withdrawing sulfur oxides and entrained desulfurizing catalyst fines from the top of the regeneration zone, withdrawing the regenerated catalyst from the regeneration zone and transferring the catalyst to the reducing zone, treating the catalyst with a reduc- [Gatalystz 10% M00; on HF-Sli. Feed: (0.15% S) H Rate 1.0 Ms.cf./b

M01 percent S in Exit Stream-Expressed as H s Pres- Feed Cycle sure, Rate, Temp., Hour p.s.i. w./hr./w F. Organic Sulfur Total Sulfur Oon- Research Sulfur (Unconverted Octane verted) to H s 4 0 27 0.0070 0.26 5 0.26 1 0.0098 0.010 2 0.00s 2 200 5 850 3 0,010 4 0.016 5 0 27 0.0029 0.27 1 0.010 2 0.004 3 200 5 900 a 0. 014 4 0. 029 0. 0027 0. 026 6 0.050 1 0. 0059 0. 0043 0. 0016 2 0. 0023 0019 0. 0004 4 200 2 900 3 0. 0004 4 nil 5 0. 0008 0.0008 nil 1 nil 2 0.0023 0.0023 nil 2 3.1 5 2 5 0. 0014 0. 0014 nil 6 n0 7 0.02 8 0.242 0.0019 0.24 1 nil 2 0.0072 0.0072 400 2 800 3 4 6 4 0.0012 0.0012 n11 5 0. 0025 0. 0013 0. 0012 6 0. 292 0. 0022 0. 99 1 0.0012 3 0.0013 0. 0013 0 7 400 5 900 4 0 222 5 0.2+ 6 0.3+ 0.0027

1 Ms.c.f./'b =thousand standard cubic feet of hydrogencontaining gas fed to desulfurizer It will be noted from the foregoing runs that the naphtha contained a very appreciable amount of sulfur, namely, 0.15% by weight. It Will further be noted, particularly, during cycles 5 and 6, that the sulfur content of this naphtha was very greatly reduced. It will further be noted in the foregoing runs, with respect to cycle 5, that during the first six hours of this run, none of the sulfur in the feed stock was converted to H 8, but rather was combined with the molybdenum catalyst.

Numerous modifications of the present invention may be made by those familiar with the art without departing from the spirit thereof.

What is claimed is:

1. A method of hydroforming naphtha containing sulfur which comprises contacting the naphtha at elevated temperatures and pressures in a hydrodesulfurization zone wtih a fluidized bed of desulfurizing catalyst selected from the group consisting of molybdenum oxide and cobalt molybdate on alumina adapted to combine chemically ing gas, withdrawing water, hydrogen sulfide, low molecular weight hydrocarbons, and entrained desulfurizing catalyst fines from the top of the reducing zone, withdrawing reduced catalyst from bottom of the reducing zone and returning the catalyst to the hydrodesulfurization zone, withdrawing a treated naphtha stream from the hydrodesulfurization zone substantially free of volatile sulfur compounds, causing said stream to pass through a plurality of solid-gas separating zones whereby entrained catalyst is substantially removed from the stream, charging the treated naphtha stream uncooled to a hydroforming zone containing a hydroforming catalyst comprising a fixed bed of supported platinum group metal, maintaining the hydroforming zone at hydroforming conditions of temperature and pressure and contact time until the desired hydroforming reaction takes place, and recovering a product of improved octane rating from the hydroforming zone.

2. The method set forth in claim 1 in which the hydroforming catalyst is platinum on alumina.

References Cited in the file of this patent UNITED STATES PATENTS I Burk et a1 June 4, 1946 8 Nicholson et a1. Oct. 22, 1946 Lee Mar. 11, 1947 Haensel et a1. Aug. '16, 1949 Haensel Aug. 16, 1949 McAfee' Dec. 23, 1952 Dickinson June 16, 1953 Rex Sept. 13, 1955 

1. A METHOD OF HYDROFORMING NAPHTHA CONTAINING SULFUR WHICH COMPRISES CONTACTING THE NAPHTHA AT ELEVATED TEMPERATURES AND PRESSURES IN A HYDRODESULFURIZATION ZONE WITH A FLUIDIZED BED OF DESULFURZING CATALYST SELECTED FROM THE GROUP CONSISTING OF MOLYBAENUM OXIDE AND COBALT MOLYBDATE ON ALUMINA ADAPTED TO ACOMBINE CHEMICALLY WITH AT LEAST A PORTION OF THE SULFUR IN THE FEED STOCK, CHARGING HYDRGEN TO THE HYDRODESULFURIZATION ZONE, PERMITTING THE NAPHTHA TO REMAIN RESIDENT IN THE DESULFURIZATION ZONE FOR A SUFFICEIENT PERIOD OF TIME TO EFFECT THE DESIRED SULFUR REMOVAL, WITHDRAWING THE DESULFURIZING CATALYST FROM THE BOTTOM OF THE HYDRODESULFURIZING ZONE AND TRANSFERRING THE CATALYST TO A REGENERATION ZONE AND THERE IN TREATING THE CATALYST WITH AN OXIDIZING GAS TO REMOVE SULFUR FROM THE CATALYST, WITHDRAWING SULFUR OXIDES AND ENTRAINED DESULFURIZING CATALYST FINES FROM THE TOP OF THE REGENERATION ZONE, WITHDRAWING THE REGENERATED CATALYST FROM THE REGENERATION ZONE AND TRANSFERRING THE CATALYST TO THE REDUCING ZONE, TREATING THE CATALYST WITH A REDUCING GAS, WITHDRAWING WATER, HYDROGEN SULFIDE, LOW MOLECULAR WEIGHT HYDROCARBONS, AND ENTRAINED DESULURIZING CATALYST FINES FROM THE TOP OF THE REDUCING ZONE, WITHDRAWING REDUCED CATALYST FROM BOTTOM OF THE REDUCING ZONE AND RETURNING THE CATALYST TO THE HYDRODESULFURIZATION ZONE, WITHDRAWING A TREATED NAPHTHA STREAM FROM THE HYDRODESULFURIZATION ZONE SUBSTANTIALLY FREE OF VOLATILE SULFUR COMPOUNDS, CAUSING SAID STREAM TO PASS THROUGH A PLURALITY OF SOILD-GAS SEPARATING ZONES WHEREBY ENTRAINED CATALYST IS SUBSTANIALLY REMOVED FROM THE STREAM, CHARGING THE TREATED NAHPTHA STREAM UNCOOLED TO A HYDROFORMING ZONE CONTAINING A HYDROFORMING CATALYST COMPRISING A FIXED BED OF SUPPORTED PLATIUM GEROUP METAL, MAINTAINING THE HYDROFORMING ZONE AT HYDROFORMING CONDITIONS OF TEMPERATURE AND PRESSURE AND CONTACT TIME UNTIL THE DESIRED HYDROFORMING REACTION TAKES PLACE, AND REHYDROFORMING ZONE. 